<!DOCTYPE html>
<html>
<head>
	<title>17-18 盒子模型</title>
<style>
	#test1 {
		width: 300px;
		height: 300px;
		background: gray;
		padding: 20px;
		border: 20px solid blue;
		margin: 20px;
	}
	#test2 {
		width: 300px;
		height: 300px;
		background: gray;
		padding: 20px;
		border: 20px solid blue;
		box-sizing: border-box;
		/*
		默认是: 内容盒
		box-sizing: 尺寸
		border-box; 内容盒
		content-box; 边框盒
		*/
		margin: 20px;
	}
</style>
</head>
<body>
	<div id="test1"></div>
	<div id="test2"></div>
</body>
</html>